1. Field of the Invention
This invention relates to drywall cutting and scoring devices which can quickly, easily, and accurately cut drywall transversely, longitudinally, and at right angles, without the need for separate measuring, marking, chalk-lining, and cutting steps.
2. Description of the Prior Art
Drywall is commonly used in place of plaster in the construction of interior walls and ceilings because it saves both time and money compared to traditional construction using wet plaster. Drywall consists of a thin layer of plaster-like material, commonly gypsum, sandwiched between two pieces of heavy paper and is available in standard widths or panels.
Because drywall panels are manufactured in standard sizes, such as four feet by eight feet or four feet by twelve feet, installers must measure and cut many pieces to fit in small spaces such as above and below windows, skylights, etc.
The drywall industry has long attempted to provide a practical tool which could minimize the marking and scoring steps associated with drywall cutting. A T-square and utility knife has proved to be useful, but is limited to cutting drywall that is exactly four feet and requires measuring and chalk-lining prior to cutting or scoring. Various attempts have been devised by inventors to overcome these shortcomings, as indicated by the prior art.
U.S. Pat. No. 5,265,342 to Lang (1992) discloses a drywall cutting device which uses friction to bind a guide to a measuring stem. While this method of locking the guide to the measuring stem might work initially, the handle is awkward for practical use and the guide would be prone to slipping with regular and repeated use. Moreover, the tool requires a special blade that would make manufacturing more expensive. Furthermore, since the guide portion is connected to the cutting element by only a single rod, the cutting element would tend to move from side-to-side while cutting, resulting in an inaccurate cut.
U.S. Pat. No. 5,083,375 to Helm (1991) shows a cutting device which is both awkward and impractical. For example, since it is understood that drywall is commonly manufactured in widths of 48 inches, cutting two inches off the wallboard would produce the same overall effect as cutting 46 inches off the wallboard. In both instances, the finished results would both be approximately the same: one piece cut at two inches and the other piece cut at 46 inches. Obviously, then, it should be evident, that the width of a drywall panel can be cut quicker, easier, and with greater precision, when working in the range of 0 to 24 inches; rather than working in the range 24 inches to 48 inches. Helm's device does not take this important fact into consideration and thus, cutting pieces greater than 24 inches would always be more difficult and less accurate. Furthermore, having to loosen and tighten a locking knob with each cut would make the tool impractical.
U.S. Pat. No. 4,949,462 to Spencer (1988) discloses a drywall cutting device which works much the same way as Helm's, and with many of the similar shortcomings; except the combined larger size of this device would make it particularly awkward for cutting very small pieces of wallboard. Small pieces of wallboard require more sensitivity and control when cutting and are more difficult to cut because the wallboard has a tendency to slip-out away from the knife.
U.S. Pat. No. 2,952,025 to Johnson (1959) combines a simple tape measure with a utility knife which is not too different from the way many installers presently cut drywall.